SUMMIT, N.J. (CBSNewYork)NJ TRANSIT riders should brace for more canceled trains.

There’s already a shortage of engineers, and now, many of them are refusing to pick up extra shifts, like filling in for people on summer vacation.

An on-time train is something NJ TRANSIT riders have learned to cherish. One passenger told CBS2’s Lisa Rozner she takes the first one into New York City and sometimes, because there’s no engineer, it never shows.

“He calls out sick or something. My train gets canceled,” she said.

Dan Tague commutes from Roxbury.

“You could be in 20 minutes late, you could be in an hour late, you never know. That’s the problem,” he said.

This weekend, more than 40 trains were canceled.

RELATED STORY: Murphy Touts New Class Of NJ TRANSIT Engineer Graduates, Says Service This Summer Will Be ‘Less Bad’

The union rep for the agency’s locomotive engineers told CBS2 by phone that most are now “choosing” not to work beyond a five-day work week, and right now, those extra shifts are needed to cover when someone calls out sick or goes on vacation.

It’s in protest of the agency allegedly offering extra money only to certain engineers, and not everyone, to work relief days for special events.

Todd Barretta was NJ TRANSIT’s chief compliance officer for half of 2017.

“Because there’s such an engineering shortage that they have to force people to violate the hours of service act. They give side jobs to those that don’t mind violating that,” he said.

After being fired, Barretta sued the agency, citing an “unsafe culture,” which he claims persists among engineers.

“They’re in such dire need of engineers … that they’ve reduced the standards of qualifying an engineer,” he said.

NJ TRANSIT refused to make anyone available to speak with CBS2 on camera. A spokesperson would only send the following statement by email:

“While working on relief days is not a contractual obligation, we are always appreciative of our engineers who go above and beyond the call of duty to fill open shifts as we diligently address the current engineer shortage. NJ TRANSIT adheres to the contract, and in that Collective Bargaining Agreement, there is a formal process in place to resolve disputes.

“In order to build ranks of engineers to better serve riders, NJ TRANSIT has increased the number of engineer training classes to a record-setting six classes running concurrently. There are four engineer classes set to graduate in 2019. Over the past year, we’ve hired more than 100 locomotive engineer trainees.”

Passengers hope if there are more cancellations, they at least get as much notice as possible.